1. Field of the Invention
One embodiment of the present invention relates to a lighting device and a method for manufacturing the lighting device.
2. Description of the Related Art
In recent years, development has been conducted on lighting using a light-emitting element which utilizes organic electroluminescence (EL) (hereinafter referred to as an organic EL light-emitting element). Since organic EL light-emitting elements can be formed in a film form, organic EL light-emitting elements can provide planar light emission and can be used as planar light sources. This is a distinctive feature that is difficult to obtain with a point light source typified by an incandescent lamp or an LED or a linear light source typified by a fluorescent lamp, and the utility value of organic EL light-emitting elements is high.
However, in the case of a light-emitting element emitting light in a region with a higher refractive index than the air, such as an organic EL light-emitting element, there is a condition under which part of light emitted from the light-emitting element is totally reflected at an interface between the air and a device including the light-emitting element. As a result, efficiency in extracting light from the inside of the light-emitting element to the air does not reach 100%.
On the other hand, as for an improvement in light use efficiency, a microlens array in which a plurality of minute lenses is arranged has been developed for the sake of collecting light in an opening of a pixel in a liquid crystal panel or collecting light in an opening of a light receiving element in a digital camera. For example, Patent Document 1 discloses a microlens array in which minute lenses are arranged on both sides and with which a display screen of a liquid crystal panel can be brightened.